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Rear wheel drive

Rear wheel drive

Submitted by sacox46 on January 18, 2011

You may want to rethink the rear wheel drive on the Model S. I guess performance on dry pavement is best with real wheel drive but that is not the case in difficult conditions. Front (and of course all wheel) drive vehicles are sooo much better in snow and ice. I would much rather be in my old Honda or even my old Plymouth van in snow than than in my current BMW. Please reconsider.

Timo |
January 30, 2012

I think I would not absolutely need AWD but it would be very useful to me. I live in a place where it is hill in every direction. Just to get out of garage is a quite steep slope. Just few days ago I watched in delighted horror how one of those crossover things with all-season tires slide sideways down (literally down) the street (got out of parking space next to my apartment and immediately started to slide). It somehow managed to not hit anything.

Having driven AWD:s, RWD:s and FWD:s in winter and actually having trained for slippery condition driving I really appreciate the extra grip AWD gives in those conditions.

(I hate tanks, they are cramped smelly and loud things. I prefer light APC:s with capability of crossing rivers and swamps).

Robert.Boston |
January 30, 2012

I asked about Tesla's performance in ice and snow at the Santana Row store today, and their answer is really clear -- the Roadster handles very well in ice and snow, and the Model S will beat or exceed that performance.

An interesting video here. I've seen others, similar, that show the Roadster coming to a full stop on a snowy hill and starting up again without even a hint of slipping.

Mycroft |
January 30, 2012

IMO, driving on snow just requires having the right tires and the right driving technique. I think the only thing FWD gives you is a little additional traction from the weight of the ICE.

BruceR |
January 30, 2012

And the battle between various drive wheel configurations continues....

As Volker points out, they all have their advantages and disadvantages. FWD cars like Mini and Mazda dominate the SCCA racing series. Move up to the big powered cars and thay are all RWD. A couple teams have tried AWD in Formula 1 for instance, but that series is dominated by RWD. Rally cars and off road races are dominated by the AWD for obvious reasons.

So it all goes back to what's most important to you. Small FWD cars are a blast to race in corners. Big powered RWD cars can be a breathtaking accelerating experience. AWD can get you out of slippery situations the others would wreck in. (And will also get you into deep doo doo when you don't understand AWD has very little assistance to braking or cornering!)

My 2 cents.

Brian H |
January 31, 2012

FWD once saved my life. I was in mountain roads, in a FWD Honda, and a corner came up suddenly that had had a recent "gravel fall", just enough to sprinkle the road with ball bearings. As I slid towards the fall-off, I instinctively lifted my foot off the gas and then "blipped" it. The wheels spun the gravel out of the way, contacted pavement, and pulled me around the corner.

That was about 40 yrs ago, and is vivid in my mind to this day.

Volker.Berlin |
January 31, 2012

And will also get you into deep doo doo when you don't understand AWD has very little assistance to braking or cornering! (BruceR)

Just thought this is worth repeating... ;-) Audi Quattros seem to fly off the corners in winter more frequently than other cars, probably due to their great traction in forward motion -- the drivers lack the sense for the real slippery outside conditions. Of course that would not happen to any members of this forum, as we are all conscious, careful and trained drivers and won't be so easily betrayed.

Timo, wrt the SUV that you watched sliding down sideways... I wonder how AWD would have helped that situation? If it is not even possible to come to a standstill, i.e., if traction is similarly close to nothing in any direction and tires even slip sideways -- the situation would only become worse when you start spinning all wheels.

Brian H |
January 31, 2012

All-seasons in snow and ice suck. Save money by not buying winter tires, and cost yourself lotsa body work, maybe for both you and your car.

Timo |
January 31, 2012

V.B, it wouldn't, but gives you (and others) a picture of what kind of place I live. I would obviously get for my Tesla car set of decent winter tires and not some slippery all season tires. I think whoever did own that car does so also in the future.

Brian H |
February 1, 2012

Happens here in Vancouver, too. Snow is rare enough that lots of the clueless have all manner of semi-comical trouble. The heavy-foot tire-spinning ices up the roads for the next guys, too.

Robert.Boston |
February 3, 2012

OK, I'm now a believer in RWD for EVs...let me explain.

On my business trip to the Bay Area this week, I rented a Nissan Altima Hybrid. Very nice car in many ways, but severely marred by the steering/handling. I could tell, absolutely, that the front wheels were simply being asked to do too much: ICE power, EV power, EV regen, braking, and steering.

Shifting some of these responsibilities to the rear would have left the front with just steering and (half of) the braking, which would have been a much better driving experience.

petero |
February 24, 2012

For the fun of it and slightly off subject, I call your attention to this You Tube vid - not all AWDs are equal.

FWD, RWD, AWD … in all cases, when driving in adverse conditions you should engage your brain and common sense.

This is the aspect that I am most nervous about, even though it will only affect me a few days a year (though potentially a lot more if I need to worry about wet roads too). I ahve never driven a RWD car.

I live and work in the Pugent Sound area around Seattle. To leave and return to my home city, I have to go down and back up large hills which are also curved. Whenever it snows, the snow usually becomes ice within the next day or two because of the mild and wet weather we have. When this happens, I always see some RWD cars and trucks which cannot climb the hills.

Does anyone know, with the Model S, or the Roadster, for that matter, to the non-drive wheels freely turn? That is, if you put the car in Drive (D), and were to lift the car off the ground, would you be able to rotate the front wheels backwards using your hands? Or does something "lock" the wheels into only turning forward. I'm not even sure if that would make a performance difference, but I'm just trying to imagine what it would be like trying to go uphill and turn at the same time in a low-traction situation.

mwu |
February 26, 2012

Th non-drive wheels usually turn freely as far as I understand it from my experience changing wheels and brakes on my cars.

Thumper |
February 26, 2012

Yes, the non-drive wheels definitely will turn freely. This is not just normal but universal on cars with drive at one end or the other.

Turns out that with its even weight distribution, long wheelbase, low center of gravity and top notch traction control, the Tesla Roadster is an excellent winter car -- and IMO it's unlikely that the Model S will be any worse.

olanmills |
February 26, 2012

Cool, thanks.

phb |
February 26, 2012

Tires, tires, tires. Get some Nokian snow tires and you'll be just dandy!

Volker.Berlin |
February 27, 2012

One detail to keep in mind: On a steep incline, weight shifts to the rear axle. With weight shifting away from the front axle, driven front wheels will increasingly less likely be able to pull it off (intentional pun). Thus, maybe counter-intuitively, the Model S RWD with its low center of gravity may actually be better in some situations than an AWD Jeep. (No doubt there are more tough-terrain situations where the AWD Jeep will have advantage over the RWD Model S.)http://www.youtube.com/watch?v=H6VLSFSMCsI

Butch |
February 27, 2012

There are two forms of "Traction Control" that are used in many cars.

One method applies the brake to the wheel that is spinning or starting to spin. Because a differential is a constant torque device that allows the wheels to turn at different speeds, if one wheel has no friction, it will spin at nearly zero torque; this then puts nearly zero torque on the wheel that has friction. If the brake is applied to the spinning wheel, this puts torque on that axel and thus puts torque on the wheel with some traction, and the vehicle can start to move. I call this real traction control.

Another form that is used in the Prius and the Tesla Roadster 1.5 that I have senses a spinning tire and then reduces torque and power from the motor to the wheel. This helps reducing spinning by applying less force, but if there is nearly zero friction on one wheel, it can be very frustrating to have nearly zero power applied to the wheels and not move. I have experienced this many times in a Prius that I used to own and the Roadster 1.5 that I currently own. BTW, I call this anti traction control.

Here is a video of getting up the driveway at my other home in the Rockies, called Hole in the Wall. The last pitch before the house and after the last turn is a 15% grade. All I want is an electric vehicle that can make it up this most of the time in the winter. Even my jeep with air lockers and good snow tires can't make it up after a 2 foot, 60 cm snowfall until its plowed. The worst case conditions are when the winter packed powder is melting in the spring and the road is covered with slushy ice. Then the only thing that will make it up my drive is my ATV with 4 tracks in place of the 4 wheels. Most of the time, if I put chains on all 4 wheels of the jeep I can make it up, but that is a serious pain...

As far as I can tell the Model S will have "Real Traction Control." The Model X has two motors, one for the front and one for the rear, somewhat like the Lexus Crossover hybrids (400h and 450h). I have driven the 400h and it is pretty good in low traction situations. If the Model X with its two motors has real traction control front and rear, it should be excellent in low traction situations.

BTW, my approach to my driveway in the jeep is to use my air lockers. They allow me to lock up or put all the differentials in solid mode, as if it had solid axels. On solid pavement, this mode is difficult to steer, and grinds up the tires, but if one wheel has traction, the jeep will move. On snow, grinding the tires is not an issue; the snow gives. The comment on tires is very true. In the winter, I only use good snow tires.

The Range Rover in the video from the last post ran out of torque, not traction. If she had put the Range Rover in low range and turned on its traction control (one of the best made), it would have gone all the way to the top, no problem. I have climbed such hills in my jeep and in Range Rover test drives. BTW, the Range Rover traction control, works on all four wheels, applying brakes to any wheel that starts to slip.

I have been assured that the Model S, competing with BMW 5 series, etc, has real traction control. I have to assume that the Model X will have real traction control front and rear. My question is do I wait 2 years for the Model X or take my Model S reservation this year...

Supergreekster |
February 29, 2012

The real question is this:

If tesla offered AWD as an option, would you consider it?

If it cost $500 and range loss was only 3%, I think we would ALL ADD THAT OPTION!!

In reality it is just a matter of how much $$ and possibly how much change in RANGE. I know I would be willing to pay a couple $k for this. Especially if the design is such that 99% of time it is RWD

Btw I drive GT-R. Great car, inspires incredible confidence with AWD and MANY MANY electronic systems for stability, grip. Including accelerometers. But during a recent FREAK snowstorm, I was able to get where I needed to go with the practically slick tires... If we had more than 3 days of snow here, I would have to buy different winter tires... I also feel much more confident in rainy conditions. But you must "drive for the conditions". I spun out my Subaru WRX pretty bad in icy conditions one day, four wheel spin BAD!! Not much traction control systems on the '03 WRX

The wife's FWD Volvo XC90 usually ends up powering ONE WHEEL when pulling out into traffic... Not at all confidence inspiring... When one wheel slips and it takes car 2-3 seconds to institute power transfer...

stephen.kamichik |
February 29, 2012

Subaru makes symmetrical AWD vehicles. Subaru demonstrates the superiority of their system on YOUTUBE.

David70 |
February 29, 2012

Sacox,

What's the weight distribution on you BMW?

Discoducky |
March 1, 2012

Saddle leather, center console and kids seats...I've give'em all up to light up all 4 tires around the track.

keithz |
May 16, 2012

@volker.berlin

Thought I'd continue the discussion here from the Canadian thread.

My viewpoint is simple. I'd like Tesla to offer a 4WD option. It's the same chassis as the Model X. So it could easily be done. Price it right and there's quite a few of us who would pay for it.

I get that you don't think it's necessary. That's fine. But there are quite a few of us that would be willing to pay for it. I fail to see why Tesla wouldn't want our money.

Volker.Berlin |
May 16, 2012

I get that you don't think it's necessary. That's fine. But there are quite a few of us that would be willing to pay for it. I fail to see why Tesla wouldn't want our money. (keithz)

No problem with that! ;-) Tesla is really trying hard to part you from as much of your money as possible. Just think of the Signature program, clever move. Similarly the Model X: Leveraging the Model S platform to significantly enlarge the target audience with relatively little incremental development efforts.

Adding AWD to the Model S looks easy enough, but for sure it does not come for free, in terms of time, money, engineering hours/head count which is more or less all the same. There is nothing that would rule out an AWD option for the Model S in principle, not even from my point of view. I think, the only reason why they do not offer it right away, is because it cannot all be done at the same time.

I am only guessing here, but between the Model X with optional AWD and the Model S without that option, there's probably a relatively small set of potential customers that would buy a Model S AWD but strictly don't consider any of the other of Tesla's offerings. That's not to say that this customer potential is negligible, but considering that they cannot do it all at the same time, it seems plausible to me that they prioritized the Model X (with AWD) over the Model S AWD.

Also keep in mind that they don't offer the Model X AWD this summer. AWD is still only an announcement for when the Model X becomes available, which buys Tesla some development time. It's not like they could take the AWD drive train from the Model X and implant it into the Model S today, simply because it does not yet exist (in terms of "production ready").

When the Model X is ready, and the AWD option for the Model X is ready, I am sure Tesla will reevaluate the cost vs. the opportunity of offering the Model S with an AWD option. It's not unlikely that they will then develop and offer that option, i.e., for the Model S 1.5 or 2.0 (if they stick with the Roadster versioning scheme).

Volker.Berlin |
May 16, 2012

I fail to see why Tesla wouldn't want our money. (keithz)

Tesla is really trying hard to part you from as much of your money as possible. (Volker.Berlin)

Cross-topic remark: Dare I mention the Tech Package? They do want our money, no doubt about that! ;-)

keithz |
May 16, 2012

@VB

Good points sir.

They could have pre-launched the AWD Model S with the Model X possibly. Oh well, time will tell.

stephen.kamichik |
May 16, 2012

They would have to redo the crash testing with an AWD model S.

brianman |
May 16, 2012

@keithz, @Volker.Berlin

I think I agree with both of you if you phrase it this way:
"Tesla should seriously consider offering AWD for Model S 2.0 (or 1.5)."

I think the difference of opinion is about whether it's wise for them to explore it for v1.

brenan_r |
March 23, 2014

I would NEVER think of buying a Tesla with FWD. If a performance car doesn't have RWD, it's not worth buying, even if it has 400 HP to start off.

Anyway, just some side thoughts: HP wise, the 400 HP is pretty nice, but because you can't just take it to any mechanic, or buy aftermarket parts to increase performance. How do I break the 500 HP??? Looks like even if it were possible, Tesla is where I would need to get the parts - and I HATE companies that try to hold a monopoly on what I buy, or tell me what I can or can't buy. I like being able to control the cost, not them. Right now, there are guys out there that took cars that cost less than a Tesla Model S and modified them to have 500, 700, or even 1000 HP. The fact that it's electrical or "Green" means NOTHING to me compared to the performance you can get out of a car.